1. Field of Invention
The present invention relates to metal and, more particularly, to a method for making absorbent for metal for use in absorbent, paint, emulsion resin, adhesive, polymeric concrete and textile paste.
2. Related Prior Art
A huge number of information products and consumer products are produced globally, with a lot of metal consumed. Hence, we are running out of reserves of metal. Moreover, such information products and consumer products are replaced with new ones rapidly so that their lives are shortened. Therefore, there is a huge amount of waste related to electronic devices that are disposed of. Such waste includes various sorts of fundamental metal and metal. There are various sources of wasted metal. The resources include mines, metallurgy, mechanical manufacturing, chemical industry, electronic industry and instruments.
Heavy metal is often toxic, acute or chronic. Sometimes, heavy metal poisons living creatures in a complicated manner to affect an entire food chain. As the study of the heavy metal and related measurement technology advance, there is a trend to process the heavy metal by higher standards. Some of the heavy metal is recycled while the other heavy metal is stabilized so that it does not impose hazard to the environment and the living creatures living in the environment.
In the past decades, synthetic macromolecular composite micro-balls have gained a lot of attention. For example, polymethylmethacrylate (“PMMA”) macromolecular micro-balls made by polymerization of methylmethacrylate monomer (“MMA”) are an important organic transparent material. PMMA is very transparent, stands various sorts of weather, exhibits balanced mechanical properties, and can easily be processed. However, PMMA does not stand heat and exhibits a low absorption rate, inadequate mechanical strength and lacks functional groups. By co-polymerization or surface modification, macromolecular micro-balls can be provided, on the surface, with various functional groups such as —COOH, —NH2, —OH, —SO3H and —CH3Cl. Thus, the macromolecular micro-balls can be provided with new functions. Hydrophile polymers provided with functional groups can easily be distributed on the surfaces of the micro-balls, thus the surfaces of the micro-balls are functionalized. Macromolecular micro-balls with the carboxylic group are suitable for various applications because the molecules of the carboxylic acid easily react with various molecules. Therefore, the macromolecular micro-balls provided with the carboxylic group gain a lot of attention. There have been various efforts to polymerize macromolecular micro-balls provided, on the surfaces, with the carboxylic group for absorbing proteins to become vaccines, adhering broken bones, processing potable water, and processing waste water. The use of the macromolecular micro-balls as absorbent is advantageously simple and inexpensive. However, the macromolecular micro-balls exhibit low absorption ratio and speed regarding metal, and only absorb a limited number of types of metal.
In 2005, Cox et al. studied the use of active carbon to absorb metal. Regarding the absorption rates, Au (III)>Pd (II)>Ag (I)>Pt (II)≈Pt (IV). The study has revealed that active carbon possess large specific area that is advantageous for absorbing metal. However, active carbon absorbs only a limited number of types of metal, and the reprocessing of active carbon is difficult.
In 2002, Say et al. used poly(HEMA-EGDMA) micro-balls and a chelating agent, 2-methacrylamidohistidine (“MAH”), for modification. The resultant product absorbs metal ions very well.
As disclosed in U.S. Pat. Nos. 5,115,036 and 5,064,879, co-polymer of ethylene with aminoalkyl acrylate includes functional groups that are electrically negative for chelating metal ions in waste water processing. It however takes a very long period of time (3 to 16 hours) to complete the reaction. Moreover, the metal ions must be removed after the reaction, and this is a big challenge for the cost of related equipment.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.